Fingerprint sensors and systems incorporating fingerprint sensors

ABSTRACT

Various embodiments of access control systems and fingerprint sensing systems are disclosed. One or more fingerprints of an authorized person are recorded in a fingerprint database together with a sequence of angular positions. The authorized person may subsequently gain access to a secured item by scanning the authorized person&#39;s finger or fingers in accordance with the sequence of angular positions. Various embodiments of fingerprint sensors for determining the angular position of a finger on the sensor are also disclosed.

FIELD

The described embodiments relate to fingerprint sensors and to systemsthat incorporate fingerprint sensors.

BACKGROUND

Various security systems require the use of biometric systems to provideaccess for an authorized person to a product, location or service or toauthenticate the presence of an authorized person at a particularlocation. For example, security locks may be configured to be releasedwhen an approved fingerprint is scanned at a fingerprint scanner. Somepersonnel tracking system require an authorized person to scan anapproved fingerprint at a fingerprint scanner to prove that theauthorized person is present at the location of the fingerprint scanner.The use of biometric such as a fingerprint to identify an authorizedperson has the advantage that the authorized person is positivelyidentified. Other persons typically do not share the same biometric.Depending on the nature of the scanner, it may be possible for anunauthorized person to present an approved fingerprint in the form of atwo or three dimensional copy such as an image or model or as part of asevered finger. Fingerprints are essentially permanent characteristicsof a person. An unauthorized person who is able to present an authorizedfingerprint can only be stopped from gaining access by de-authorizingthe fingerprint.

Some security systems avoid the problem of using an immutable biometricof an authorized person by using a passcode such as a password or asequence of gestures. The passcode may be issued for use by anauthorized person, and may be cancelled or replaced as needed when aperson is no longer authorized or as a new passcode is needed. Inaddition a passcode has the advantage that it can be memorized orotherwise recorded by a person but is not an immutable physicalcharacteristic. A passcode can be changed as needed. However, passcodessuffer from the problem that they can be stolen using keyloggers,cameras or guessed by unauthorized persons. Passcodes can also bedisclosed to an unauthorized person through carelessness orinadvertence.

SUMMARY

It is desirable to provide security systems and methods that have boththe positive identification provided by the use of a biometric and theflexibility provided by the use of a passcode. The embodiments describedbelow provide such systems and methods, thereby allowing positiveidentification of an unauthorized person while also requiring theauthorized person to input or enter a passcode to gain access or toauthenticate the presence of an unauthorized person at a location.

In a first aspect, some embodiments provide a fingerprint sensing systemcomprising: fingerprint sensor having: sensor die; a die connectionlayer coupled to the sensor die; and two or more drive signal injectionpoints, wherein each signal injection point is electrically isolatedfrom the sensor die; and a controller coupled to the drive signalinjection points for injecting a drive signal into each drive signalinjection point and to the die connection layer for receiving afingerprint signal from the sensor die, wherein the fingerprint signalcorresponds to less than all of the drive signals.

In some embodiments, the fingerprint sensor includes a bezel and whereinthe drive signal injection points are positioned on the bezel.

In some embodiments, the signal injection points are formed in acontinuous bezel at least partially surrounding the sensor, such that afinger may be positioned in contact with the sensor die and one of thesignal injection points to couple a drive signal from the signalinjection point to the sensor die.

In some embodiments, the bezel is grounded between adjacent signalinjection points.

In some embodiments, the system further includes a segmented bezelhaving bezel segments that are electrically isolated from one another,wherein each bezel segment includes a signal injection point and when afinger is positioned in contact with both the sensor die and one of thebezel segments, a drive signal is coupled from the bezel segment to thesensor die.

In some embodiments, the controller is configured to determine an anglecorresponding to the fingerprint signal.

In some embodiments, the angle corresponds to the position of one ormore drive signal injection points.

In some embodiments, the fingerprint signal corresponds to one of thedrive signals.

In some embodiments, the bezel includes finger positioning guidescorresponding to the position of the drive signal injection points.

In another aspect, some embodiments provide a method of authorizing anaction, the method comprising: providing a plurality of authenticationsequences, wherein each authentication sequence comprises: an authorizedperson identifier; two or more sequential angular positions; providing aplurality of authorized person records, wherein each person recordincludes: a person record identifier; and a fingerprint record; two ormore sequential angular positions; sensing a fingerprint; identifying aperson by comparing the sensed fingerprint to fingerprint records in oneor more person records; determining an angular fingerprint positioncontemporaneously with the sensing the fingerprint; repeating the stepsof sensing, identifying and determining at least once and, for eachiteration, recording the identified person and the angular position ifthe identified person for each iteration, and if identified person ineach iteration corresponds to an authorized person and recorded sequenceof angular positions corresponds to the same authorized person, thenauthorizing the action.

In various embodiments, fingerprint sensing systems and access controlsystems may operate in a low power normal operation modes. In someembodiments, the systems may be combined with other access control andauthentication systems, such as magnetic or RFID cards and tags.

In another aspect, some embodiments provide a method of operating anaccess control system, the method comprising: recording fingerprint datacorresponding to one or more fingers of a particular authorized person;recording a sequence of finger positions for the particular authorizedperson; receiving a series of fingerprint signals from a fingerprintsensor; determining a sequence of angular positions corresponding tosequential fingerprint signals in the series; determining if each of thefingerprint signals corresponds to the recorded fingerprint data;determining if the sequence of angular positions corresponds to therecorded sequence of finger positions; and if the fingerprint signalscorresponds to the recorded fingerprint data and the sequence of angularpositions corresponds to the recorded sequence of fingerprint positions,then providing an authorization signal.

In some embodiments, the authorization signal includes an identificationof the authorized person.

In some embodiments, the sequence of finger positions is specified bythe authorized person.

In some embodiments, the fingerprint data corresponds to one or morefingers of the authorized person positioned in multiple angularpositions on a fingerprint sensor.

In some embodiments, the fingerprint data corresponds to one or morefingerprints of the authorized person in a standard orientation.

In some embodiments, the fingerprint data and the sequence of fingerpositions of the particular authorized person are recorded in anauthorized person record in a fingerprint database that containsauthorized person records for a plurality of authorized persons.

In some embodiments, the method includes requiring the particularauthorized person to identify himself or herself prior to providing theauthorization signal.

In another aspect, some embodiments provide a method of operating anaccess control system, the method comprising: recording fingerprint datacorresponding to one or more fingers of a particular authorized personrotated at a variety of angles on a fingerprint sensor; recording asequence of angular finger positions for the particular authorizedperson; receiving a series of fingerprint signals from a fingerprintsensor; and if each of the fingerprint signals corresponds to therecorded fingerprint data and to the sequence of angular fingerpositions, then providing an authorization signal.

In some embodiments, the authorization signal includes an identificationof the particular authorized person.

In some embodiments, the sequence of finger positions is specified bythe particular authorized person.

In some embodiments, the fingerprint data and the sequence of fingerpositions of the particular authorized person are recorded in anauthorized person record in a fingerprint database that containsauthorized person records for a plurality of authorized persons.

In some embodiments, the method includes requiring the particularauthorized person to identify himself or herself prior to providing theauthorization signal.

In another aspect, some embodiments provide a method of operating afingerprint sensing system, the method comprising: providing afingerprint sensor having a sensor die and a bezel, wherein the bezelhas a plurality of drive signal injection points; injecting a drivesignal into each of the drive signal injection points;

receiving a fingerprint signal from the fingerprint sensor, wherein thefingerprint signal corresponds to at least one of the drive signals; anddetermining the drive signal or drive signals to which the fingerprintsignal corresponds.

In some embodiments, the drive signal injection points are spaced aboutthe bezel.

In some embodiments, the drive signal injection points are located atvarious angular positions about the bezel.

In some embodiments, the method includes varying the magnitude of someor all of the drive signals to control a signal-to-noise ratio of thefingerprint signal.

In some embodiments, the method includes varying the magnitude of someor all of the drive signals to control lines and gaps in a fingerprintimage obtained from the fingerprint signal.

In some embodiments, the method includes determining an angularorientation of a finger positioned on the fingerprint sensor.

In some embodiments, the method includes repeating the steps ofreceiving a fingerprint signal and determining the drive signal or drivesignals to which the fingerprint signal corresponds and furtherincluding recording a sequence of drive signals corresponding to thereceived fingerprint signals.

In some embodiments, the drive signals are different from one another.

In some embodiments, the drive signals have temporally distinct activeand inactive phases.

In some embodiments, the drive signals have different shapes, each ofwhich is distinguishable from the other drive signals.

In another aspect, some embodiments provide a fingerprint sensing systemcomprising: fingerprint sensor including: a bezel having a plurality ofsignal injection points; a sensor die electrically insulated from thebezel; and a controller coupled to the fingerprint sensor to receive afingerprint signal, wherein the controller includes: a plurality ofdrive signal blocks, wherein each drive signal block is coupled to acorresponding signal injection point to inject a drive signal into thecorresponding signal injection point.

In some embodiments, the bezel and sensor die are positioned to alloweach of the drive signals to be coupled to the sensor die by a finger incontact with the corresponding drive signal injection point and thesensor die.

In some embodiments, each drive signal is unique.

In some embodiments, each of the drive signals has an active phase andan inactive phase, wherein only one drive signals is in an active phaseat any particular time.

In some embodiments, the controller and the fingerprint sensor arecoupled through a wired communication link.

In some embodiments, the controller and the fingerprint sensor arecoupled through a wireless communication link.

In some embodiments, the bezel is formed of a conductive material.

In some embodiments, the bezel is formed of a conductive materialselected from the group consisting of conductive plastics and metal.

In some embodiments, the bezel is a continuous bezel.

In some embodiments, the bezel is a continuous bezel and wherein thebezel is grounded between at least some adjacent signal injectionpoints.

In some embodiments, the bezel is a segmented bezel formed of aplurality of bezel segments and wherein at least some of the signalinjection points are provided on different bezel segments.

In some embodiments, the bezel is a segmented bezel formed of aplurality of bezel segments and wherein at least some of the signalinjection points are provided on different bezel segments.

In some embodiments, the bezel is grounded between at least someadjacent signal injection points.

In some embodiments, the bezel is a segmented bezel and wherein eachsignal injection point is provided on a different bezel segment.

In another aspect, some embodiments provide an access control systemcomprising: a fingerprint sensor; a controller coupled to thefingerprint sensor; and a fingerprint database coupled to thecontroller, wherein the fingerprint database includes a plurality ofauthorized person records, each of the authorized person recordscontaining fingerprint data corresponding to an authorized person and anauthorized angle sequence.

In some embodiments the fingerprint data includes data corresponding toone or more of the particular authorized person's fingerprintspositioned at a plurality of angular positions on the fingerprintsensor.

These and other aspects of the invention as discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will now be described indetail with reference to the drawings, in which:

FIG. 1 is a partial cutaway drawing of a fingerprint sensing system;

FIG. 2 is another view of the system of FIG. 1;

FIG. 3 is a timing diagram illustrating some signals in the system ofFIG. 1;

FIG. 4 is a block diagram of a controller of the system of FIG. 1;

FIG. 5 illustrates a fingerprint sensor of the system of FIG. 1 in use;

FIGS. 5 a-5 h illustrate a finger positioned on a fingerprint sensor atvarious angular positions;

FIG. 6 is a block diagram of another fingerprint sensing system;

FIG. 7 is a block diagram of another fingerprint sensing system;

FIG. 8 is a timing diagram illustrating some signals in the system ofFIG. 7;

FIG. 9 is a block diagram illustrating an access control system;

FIG. 10 is a flowchart illustrating a method of creating records in afingerprint database;

FIG. 11 is a flowchart illustrating a method of permitting an authorizedperson to access an item;

FIG. 12 is a block diagram illustrating another access control system;

FIG. 13 is a block diagram illustrating another access control system;

FIG. 14 illustrates a fingerprint;

FIGS. 15 a and 15 b illustrate a fingerprint in various conditionsduring a person's heartbeat;

FIG. 16 a-16 c are, respectively, isometric, top and side views of afingerprint sensor; and

FIGS. 17-19 illustrate several low-power fingerprint sensing systems.

It will be understood that the drawings are exemplary only. Allreference to the drawings is made for the purpose of illustration onlyand is not intended to limit the scope of the embodiments describedherein below in any way. For convenience, reference numerals may also berepeated (with or without an offset) throughout the figures to indicateanalogous components or features.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference is first made to FIGS. 1 and 2, which illustrate a firstembodiment of a fingerprint sensing system 100. System 100 includes afingerprint sensor 102 and a controller 104.

Fingerprint sensor 102 includes a bezel 106, a sensor die 108,insulation 110 and a die connection layer 112. Bezel 106 is a continuousresistive ring having a plurality of signal injection points 114 a-114h. The bezel 106 is grounded between each pair of adjacent signalinjection points 114. Each injection point 114 has a corresponding drivesignal connection 116 a-116 h. In various embodiments, the bezel may beformed of various conductive materials, including conductive plastics,metal and other materials.

Controller 104 is coupled to sensor 102 through a cable 118 and cable120. Controller 104 includes a processor 116, a plurality of drivesignal blocks 122 a-122 h and a signal sensor block 124. Cable 18 may bea multi-conductor cable or a parallel or serial communications cable orany other type of communication link. In some embodiments, thecontroller and sensor may be coupled through a wireless communicationlink. Processor 116 may be any type of programmable processing deviceincluding a programmed computer, a microcontroller, a logic array suchas a programmed gate array or field programmable gate array, aprogrammable logic controller, a central processing unit, a digitalsignal processor, a general purpose computer, a microprocessor or anyhardware or software device capable of controlling system 100 to operateas described herein.

Each drive signal block 122 is coupled to a corresponding signalinjection point 114 through cable 118. Die connection layer 112 iscoupled to signal sensor block 124 through cable 120.

Referring also to FIG. 3, each drive signal block 122 a-122 h generatesa drive signal 126 a-126 h that is injected into the correspondingsignal injection point 114 a-114 h. Each drive signal 126 a-126 h isunique, in that it is distinguishable from each other drive signalinjected into the fingerprint sensor 102. In this embodiment, each drivesignal 126 has an active phase 128 and an inactive phase 129. Each drivesignal is synchronized to a common time base so that no more than one ofthe signals is active at any particular time. In this embodiment, eachdrive signal 126 a-126 h has a corresponding time slot 130 a-130 hduring which it has its respective active phase. During the time slots130 allocated to other drive signals 126, each drive signal is in itsinactive phase. In this embodiment, during the inactive phase, eachsignal has a magnitude of 0. During the active phase, each drive signalis a 1 MHz square wave with a 1 volt peak to peak magnitude.

Referring to FIG. 4, each drive signal block 122 a-122 h includes asignal generation block 134 a-134 h and an amplifier 136 a-136 h. Eachsignal generation block 134 a-134 h generates a drive signal waveform138 a-138 h, which in this embodiment is a square wave. Each amplifier136 a-136 h is coupled to processor 116, which generates a gain controlsignal 140 a-140 h for to each signal generation block 122 a-122 h. Eachamplifier 136 generates the corresponding drive signal 126 byselectively amplifying the corresponding square wave 138 in response tothe corresponding gain control signal 140.

Referring to FIG. 3, gain control signal 140 a has a magnitude greaterthan zero during time slot 130 a and a magnitude of zero during timeslots 130 b-130 h. When the gain control signal 140 a is 0, thecorresponding drive signal 126 a, amplifier 136 a generates drive signal126 a with a magnitude of 0. When gain control signal 140 a is non-zero,amplifier 136 generates drive signal 126 a such that it is an amplifiedversion of square wave 138 a. The amplification factor is determined bythe magnitude of the gain control signal 140 a, allowing the processor116 to control the magnitude of the drive signal 126 a. Each of thedrive signals 126 a-126 h is generated in a corresponding manner suchthat the magnitude and timing of each of the drive signals is controlledby processor 116.

In some embodiments, the gain control signals may be digital signalswith high and low values. When a gain control signal has a high value,the corresponding drive signal waveform is output as a drive signal.When the gain control signal has a low value, the drive signal has azero output. In embodiments where the drive signals are notdistinguished based on time slices or time slots, the gain controlsignal may provide an amplification value. In embodiments where thedrive signals are not distinguished based on time slices or time slotsand it is not desired to control the magnitude of the drive signal, thedrive signal waveform generated by the signal generation block may beoutput as a drive signal.

Referring again to FIGS. 1 and 2, each drive signal 126 is injected intothe corresponding signal injection point 114 through cable 118. Bezel106 is conductive and the injected drive signals propagate into andthrough the bezel 106. Bezel 106 is grounded between signal injectionpoints limiting the portion of the bezel 106 into which a drive signalinjected at a particular signal injection point 114 propagates. Forexample, drive signal 126 c injected at signal injection point 114 c maypropagate primarily through region 144. Similarly, drive signal injectedat other signal injection points 114 propagate through regions of thebezel adjacent the signal injection points.

Reference is next made to FIG. 5, which illustrates system 100 in use. Aperson's finger 142 is illustrated on the fingerprint sensor 102. Finger142 is in contact with bezel 106 in region 144, through which drivesignal 126 c propagates. Finger 142 is also in contact with the sensordie 108, such that a fingerprint 146 on the finger 142 is pressedagainst the sensor die.

Finger 142 is conductive. Drive signal 126 c is coupled into finger 142from region 144 of bezel 106. The drive signal 126 c is then coupledfrom finger 142 to sensor die 108. Insulation 110 is positioned betweenbezel 106 and sensor die 108 to prevent drive signals from beingdirectly from the bezel to the sensor die. A dermal layer of the finger142 is charged by the drive signal 126 c coupled into it (while thedrive signal is at a non-zero level).

Sensor die 108 is a capacitive sensing element with a two-dimensionalarray of sensing elements 150 (FIG. 1). The conductive dermal layer ofthe finger 142 and the sensor die form the plates of an effectivecapacitor, which is charged by the drive signal coupled into the finger.Between the dermal layer and the sensor die is a non-conductiveepidermal layer of skin on the finger 142, in which ridges and valleysof the fingerprint 146 are formed. The epidermal layer and air withinthe valleys of the fingerprint provide a dielectric layer for theeffective capacitor. Each sensing element 150 senses a charge from theadjacent portion of the finger 142 and provides a charge intensitysignal corresponding to the intensity of the charge. The sensed chargeat different sensor elements differs depending on the presence of aridge in the fingerprint or air in a valley in the fingerprint. The dieconnection layer receives the charge intensity signals from each sensorelement and transmits a fingerprint signal 152 to the processor 116.Typically, die connection layer is coupled to each sensor element 150and includes a processing element to generate fingerprint signal 152.The operation of the sensor die and die connection layer are notdescribed in detail here as a skilled person will understand theoperation of a capacitance based fingerprint sensing element. Processor116 receives the fingerprint signal and forms a fingerprint image 154corresponding to the fingerprint 146.

The fingerprint signal 152 corresponds to both the fingerprint 146 andto the particular drive signal 126 coupled from the bezel 106 into thesensor die 108. In system 100, the charging signals 126 a-126 h havetemporally spaced active phases. Finger 142 will be charged only when itis in contact with a region of the bezel 106 in which a non-zero drivingsignal is injected (or propagated). As a result, fingerprint signal 152will contain information about fingerprint 146 only while drive signal126 c is in its active phase. At other times, drive signal 126 c is inits inactive phase and does not charge finger 142. Although the otherdrive signals 126 a-126 b and 126 d-126 h also have active phases andare injected in the bezel, these drive signals are essentially preventedfrom being coupled into finger 142 by the ground connections on bezel106 between their respective signal injection points 114. As a result,fingerprint signal 152 will contain data corresponding to fingerprint146 during the active phase of drive signal 146 c. At other times,fingerprint signal 152 will not typically contain data corresponding toa fingerprint.

Processor 116 controls the operation of system 100 such that drivesignals 126 are transmitted repetitively to the fingerprint sensor 102and fingerprint signal 152 is transmitted repetitively to the processor116. Typically, the active phase of each drive signal may be transmittednumerous times per second. In various embodiments, the active phase ofeach signal may be transmitted 10 or more times, and possibly severalhundred or more times per second. During the active phase of a drivesignal that is coupled to a finger 142, the fingerprint signal 152 maybe analyzed to identify the presence of a finger and to obtain afingerprint image 154.

Referring to FIGS. 2 and 3, processor 116 is able to determine whichdrive signal 126 that is being coupled to finger 142 based on the timeat which the fingerprint signal 152 contains data corresponding to afingerprint. Based on the coupled drive signal 126, processor 116 maydetermine the angular position of the finger. For example, in FIG. 5,finger 142 is at a 90 degree position.

Reference is made to FIG. 14, which illustrates a fingerprint 1400.Fingerprint 1400 includes varies lines 1402 and gaps 1404 thatcorrespond to the ridges and valleys in a person's fingerprint. Thelines and gaps are formed because ridges in the fingerprint couple moreenergy from a drive signal into sensing elements 150 of sensor die 108than do the valleys. If the magnitude of the drive signal is too high,then the lines may be formed too wide, with small or no gaps betweenthem. If the magnitude of the drive signal is too low, then the lines1402 may be faint or missing. In some embodiments, the processor 116 mayvary the magnitude of some or all of the gain control signals inresponse to the fingerprint signal 152. The processor may vary gaincontrol signals 140 to control the signal-to-noise ratio or to controlthe density of lines 1402 and gaps 1404 in the fingerprint. In otherembodiments, the processor may be able to control the drive signal blockto vary the frequency or shape of some or all of the drive signals toimprove a fingerprint image.

Referring to FIGS. 5 a-5 h, finger 142 is illustrated with the tip ofthe finger pointed in various directions. The drive signal coupled intofinger 142 in each position is as follows:

Figure Finger positions Drive Signal 5a  0 degrees 126a 5b  45 degrees126b 5c  90 degrees 126c 5d 135 degrees 126d 5e 180 degrees 126e 5f 225degrees 126f 5g 270 degrees 126g 5h 315 degrees 126h

Reference is next made to FIG. 6, which illustrates another fingerprintsensing system 600. System 600 is similar to system 100 andcorresponding components are identified by similar reference numerals.

The fingerprint sensor 602 of system 600 has a segmented bezel comprisedof bezel segments 606 a-606 h, rather than the continuous bezel 106 ofsystem 100 (FIG. 1). Each bezel segment 606 has a signal injection point614 a-614 h, which is coupled to controller 604 to receive a drivesignal 626 a-626 h (not shown). System 600 operates in a similar mannerto system 100. Controller 604 generates and injects drive signals 626a-626 h into each bezel segment. Like system 100, each of the drivesignals has an active phase and an inactive phase such that the activephase of each drive signal occurs during the inactive phase of each ofthe other signals. The bezel segments 606 are electrically insulatedfrom one another by insulator 610 so that the drive signal 626 injectedinto each bezel segment does not propagate into any other bezel segmentthrough the insulator 610. When a finger is placed on the fingerprintsensor 602 touching one of the bezel segments 606 and the sensor die608, the drive signal 626 coupled to that bezel segment 606 is coupledinto the finger and then into the sensor die 608. The die connectionlayer 612 produces a fingerprint signal 652 that is transmitted to theprocessor 616 through cable 620. As described above in relation tosystem 100 (FIG. 1), processor 616 may be configured to determine theangular position of the finger by determining which drive signal 626 wascoupled to the sensor die 608.

Referring briefly to FIG. 1, in system 100, it may be possible for adrive signal 126 to propagate beyond the immediate region of itscorresponding signal injection point 114, depending on the groundconnections between signal injection points and the conductivity of thebezel 106. The bezel segments 606 of system 100 provide a greater degreeof isolation between drive signals since the bezel segments are isolatedfrom one another.

In systems 100 and 600, the active phases of each of the drive signalsare spaced in time so that the specific drive signal coupled to therespective sensor dies may be determined based on the time slot in whichthe fingerprint signal contains fingerprint data.

Reference is next made to FIG. 7, which illustrates a fingerprintsensing system 700. System 700 is similar to system 600 andcorresponding components are identified by similar reference numerals.In system 700, the drive signals 726 a-726 h are distinguishable bytheir distinct shapes, but do not have temporally distinct active andinactive phases. Referring to FIG. 8, the drive signals 726 havedifferent shapes, each of which is distinguishable from the other drivesignals. Each drive signal 726 a-726 h is injected into thecorresponding bezel segment 706 a-706 h during operation of system 700.A finger positioned in contact with one of the bezel segments 706 andthe sensor die 708 will couple the corresponding drive signal 726 fromthe bezel segment into the sensor die.

Drive Signal Shape 726a High frequency square wave 726b Low frequencysquare wave 726c High frequency sine wave 726d Low frequency sine wave726e High frequency square wave with missing high pulse 726f Lowfrequency square wave with missing high pulse 726g High frequency sinewave with missing pulse 726h Low frequency sine wave with missing pulse726i High frequency square wave with missing low pulse 726j Lowfrequency square wave with missing low pulse

Referring again to FIG. 7, the fingerprint sensor 702 may be similar tofingerprint sensor 102 or fingerprint sensor 602. Controller 704, whichincludes drive signal blocks 722 a-722 j, generates drive signal 726a-726 j, and injects them into fingerprint sensor 702. Fingerprintsensor 702 has ten drive signal injection points (not shown), andgenerates a fingerprint signal 752 corresponding to one of the drivesignal 726 a.

Each drive signal block 722 includes a fingerprint signal filter 756.Each fingerprint signal filter 756 a-756 j receives the correspondingdrive signal 726 a-726 j and the fingerprint signal 752. Eachfingerprint signal filter 756 a-756 j compares its respective drivesignal 726 a-726 j with the fingerprint signal 752 and generates a matchsignal 758 a-758 h. Each match signal 758 a-758 j reflects the degree towhich the fingerprint signal 752 corresponds to the respective drivesignal 726 a-726 h. In this embodiment, each match signal 758 has avalue between 0 and 255. The match signal 758 generated by eachfingerprint signal filter 756 will have a value at or close to 0 ifthere is no or little correspondence between the respective drive signal726 and the fingerprint signal 752. The match signal 758 will have avalue at or close to 255 if there is high or exact correspondencebetween the respective drive signal 726 and the fingerprint signal 752.The fingerprint signal filter will typically, but not necessarily, beconfigured to take into account an appropriate time delay (which may bevariable and automatically determined) between the generation of thedrive signal 726 and the fingerprint signal 752. Each of the matchsignals 758 is transmitted to the processor 716. Typically, thefingerprint signal 752 will correspond to one of the drive signals 726to a higher degree than the other drive signals.

Typically, a drive signal 726 will be coupled to sensor die 708 (notshown) when a finger is placed on the fingerprint sensor 702. Processor716 utilizes the match signals 758 to determine the angular orientationof the finger. Processor 716 may be configured to do so in various ways.For example, in this embodiment, the processor 716 is configured toassume that the match signal having the largest magnitude corresponds tothe angular orientation of the finger. In other embodiments, theprocessor may be configured to determine a weighted average of the matchsignal values and estimate an angular position based on the relativemagnitudes of the match signals. In some embodiments, match signalshaving a valued below a threshold may be ignored in calculating theweighted average. This may be particularly relevant in embodiments wherethe drive signal injection points are positioned sufficiently closelythat more than one drive signal injection point is coupled to the sensordie by a finger. The specific angular position of the finger may beestimated by calculated a weighted average of the match signalcorresponding to the two or more drive signals reflected in theresulting fingerprint signal.

Reference is next made to FIG. 9, which illustrates an access controlsystem 900 for controlling access to an item such as an activity,system, location, facility, data or another item that a person may wishto access. System 900 includes a fingerprint sensor 902, a controller904 and a fingerprint database 960, an input device 962 and an outputdevice 964. Fingerprint sensor 902 and controller 904 may correspond tosystem 100, 600 or 700.

Controller 904 includes a processor 916, which is coupled to database960. Processor 916 is also coupled to an authorization terminal 966 atwhich the processor 916 provides an authorization signal 968.

Fingerprint database 960 includes a plurality of authorized personrecords, wherein each authorized person record includes:

Field Contents Authorized person An identifier for an authorized personidentifier Angle A fingerprint An image of the authorized person'sfinger rotated at angle A. Angle B fingerprint An image of theauthorized person's finger rotated at angle B. Angle C fingerprint Animage of the authorized person's finger rotated at angle C. Angle Dfingerprint An image of the authorized person's finger rotated at angleD. Angle E fingerprint An image of the authorized person's fingerrotated at angle E. Angle F fingerprint An image of the authorizedperson's finger rotated at angle F. Angle G fingerprint An image of theauthorized person's finger rotated at angle G. Angle H fingerprint Animage of the authorized person's finger rotated at angle H. Authorizedangle A sequence of angular positions. sequence

The person record identifier field corresponds to a person. Each anglefingerprint field may record an image or other data corresponding to theperson's fingerprint (typically of a specific finger such as the indexfinger) positioned on a fingerprint sensor. The authorized anglesequence is a sequence of angular finger positions.

Input device 962 may be a keyboard, keypad, mouse, touchscreen or otherdevice that may be used by a person to provide input to processor 916.Output device 964 may be a display screen or other device that providesvisual and/or audio output to a person using system 900.

Reference is next made to FIG. 10, which illustrates a method 1000 bywhich each record in the fingerprint database is populated. Method 1000is performed under the control of processor 916, which may communicatewith a person using the input device 962 and the output device 964.

Method 1000 begins in step 1002 in which an authorized person record iscreated for a person. An authorized person identifier is recorded forthe person. In some embodiments, the authorized person identifier may begenerated automatically by processor 916. In other embodiments, theperson may enter an authorized person identifier using the input device962. The authorized person identifier is recorded in the authorizedperson identifier field. The authorized person identifier for eachperson record in the fingerprint database is unique.

Method 1000 then proceeds to step 1004, in which the person positionshis or her finger on the fingerprint sensor 902 with the tip of thefinger at a 0° position (angle A). Processor 916 receives a fingerprintsignal 952 and determines (i) the angular position of the person'sfinger and (ii) an image (or corresponding data) of the person'sfingerprint. If the angular position corresponds to angle A, then thefingerprint image is recorded in the angle A fingerprint field. If theangular position does not correspond to angle A, then the person'sfingerprint may be rescanned, or alternatively, method 1000 may end.When the person's fingerprint has been recorded in angle A, method 1000proceeds from step 1004. In some embodiments, the person may be requiredto record fingerprint data for each angle A-H. In other embodiments, theperson may be permitted to skip some or all of the angles A-H. If theperson is permitted to skip angle A, and chooses to do so, method 1000may proceed from step 1004.

Following step 1004, method 1000 proceeds to step 1006 (unless method1000 was terminated during step 1004) in which the person's fingerprintis recorded with his or her finger positioned at angle B, the person ispermitted to skip angle B or the method ends.

In this manner, method 1000 proceeds through steps 1004 to 1018 in whichthe person's fingerprint is recorded at angles A-H, or in at least someof the angles A-H.

Following step 1018, method 1000 proceeds to step 1020 in which theperson is permitted to specify a sequence of fingerprint positions. Forexample, the person may specify the sequence ADHC. This sequence isrecorded in the authorized angle sequence field.

Method 1000 then ends. A person who has a record in fingerprint database960 may be referred to as an authorized person.

Method 1000 is repeated for a plurality of persons.

Reference is next made to FIG. 11, which illustrates a method 1100 bywhich system 900 may be used to permit an authorized person to access anactivity or device, access data or for some other purpose.

Method 1100 begins in step 1102, in which the person positions his orher finger on fingerprint sensor 902. Processor 916 receives fingerprintsignal 952 and determines (i) the angular position of the person'sfinger and (ii) a fingerprint image (or corresponding data) of theperson's fingerprint. Processor 916 then compare fingerprint image tothe fingerprint data recorded in the fingerprint database 960. If thefingerprint image corresponds to any recorded fingerprint, the processorthen compares the angular position of the fingerprint image to theangular position of the corresponding recorded fingerprint. If the twoangular positions match, then the processor records the angular positionas the first angular position in a sequence of angular positions. Theprocessor also records the authorized person identifier in theauthorized person record in which the corresponding recorded fingerprintwas found.

Method 1100 then proceeds to step 1104 in which the processor 916determines if the sequence of angular positions is complete. If thesequence is complete, then method 1100 proceeds to step 1106. If thesequence of angular positions is not complete, then method 1100 returnsto step 1102. In some embodiments, each authorized angle sequencerecorded in the fingerprint database 960 may be of a predeterminedlength and step 1102 is repeated until the sequence of angular positionsand corresponding authorized person identifiers has reached thepredetermined length. In other embodiments, the person may indicatewhether he or she wishes to add another angular position to thesequence. If so, method 1100 returns to step 1102. If the personindicates that the sequence is complete, then method 1100 continues tostep 1106.

In step 1106, the processor 916 determines if the authorized personidentifier recorded for each angular position in the recorded sequenceis the same. If so, the authorized person identifier may be referred toas a candidate authorized person identifier and method 1100 continues tostep 1108. Otherwise, method 1100 reports an error in step 1110 andends. The error reported in step 1110 may indicate that the sequence hasnot been entered by an authorized person, that the sequence is invalidor may provide another message.

In step 1108, the processor 916 compares the sequence of angularpositions recorded in iterations of step 1102 with the authorized anglesequence recorded in the authorized person record corresponding to thecandidate authorized person identifier. If the sequence of angularpositions matches the authorized angle sequence the candidate authorizedperson is authenticated as the authorized person corresponding to theauthorized person record and method 1100 proceeds to step 1112.Otherwise, method 1100 proceeds to step 1110.

In step 1112, processor 916 transmits an authorization signal 968indicating that the person should be permitted to access an activity,device, data or receive some other access corresponding to the candidateauthorized person identifier.

For example, system 900 may be used to control access to an item such asa facility, a car wash, or data such as a bank account or other account.An authorized person must sequentially scan his or her finger using thefingerprint scanner 902 with the finger positioned in the correctangular positions, corresponding to the authorized angle sequence in theauthorized person record for that person. If the person does sosuccessfully, processor 916 transmits an authorization signal 968allowing the authorized person to access the facility, activity, data orother item that is protected by the system 900.

In system 900, the authorized person is not required to identify him orherself prior to scanning his or her finger for the first time in step1102. The person's identity is assumed to correspond to the authorizedperson identifier that corresponds to each fingerprint scan. (If eachfingerprint scan does not correspond to the same authorized personrecord and to the same authorized person identifier, then method 1100exits following step 1106.) Such a system may be used to allow accesswhen the item being accessed is not specific to the authorized person,but is secured to prevent unauthorized persons from accessing it. System900 may also be used to control access to an item that is specific tothe authorized person, such as access to a bank account at an automatedteller machine (ATM). In such an embodiment, a person who isauthenticated as an authorized person using method 1100 is given accessto an account corresponding to the authorized person identifiercorresponding to each fingerprint scan in step 1102.

In other embodiments, a person may be required to identify him orherself prior to step 1102. For example, the person may be required toenter in an authorized person identifier or other data that can becorrelated by processor 916 to an authorized person identifier. In someembodiments, the authorized person may identify himself by presenting anidentification card, tag (such as an RFID tag), bar code or otheridentification code or device to an appropriate scanner. Typically, thescanner will be located with the fingerprint scanner 902 and coupled tothe controller 904 to allow the authorized person record correspondingto the identification code or device to be identified and accessed. Eachfingerprint scan made in step 1102 must correspond to fingerprint datarecorded in the corresponding authorized person record in order for theperson to receive access.

In system 900, the fingerprint database 960 is accessible to controller904. In other embodiments, it may be desirable to allow the fingerprintdatabase to be accessed from a plurality of locations and systems.

Reference is next made to FIG. 12, which illustrates another accesscontrol system 1200. Access control system 1200 is similar to accesscontrol system 900 and similar components are identified bycorresponding reference numerals. Access control system 1200 includes aplurality of access control modules 1270, each of which comprises afingerprint scanner 1202, a controller 1204, an input device 962 and anoutput device 964. Each controller 1204 is coupled to a fingerprintdatabase 1260 through a communication network 1271. Fingerprint database1260 may be located at a central location while some or all of theaccess control modules are located remotely from the fingerprintdatabase 1260. Communication network 1271 may be any type ofcommunication network. In some embodiments, one or more access controlmodules 1270 may be coupled directly to the fingerprint database.

Access control system 1200 may be used to control access for a pluralityof authorized users to a system from a plurality of locations. Forexample, system 1200 may be used to control access to ATMs. A bank mayintegrate an access control module 1270 into some or all of its ATMs. Acustomer of the bank may register for ATM access to the customer's bankaccounts by attending at a bank location and using an access controlmodule 1270 at the bank location to create an authorized person recordin the fingerprint database 1260 in accordance with method 1000 (FIG.10). Subsequently, the person may authenticate himself or herself at anATM using method 1100 (FIG. 11). When the customer successfullycompletes method 1100, the customer is permitted to access bankingactivities at the ATM. In some embodiments, the processor (not shown) inthe controller 1204 may also control other operations at the ATM. Inother embodiments, the controller 1204 may generate an authorizationsignal that is coupled to a controller for other ATM functions. Theauthorization signal may indicate the identity of the authorizedcustomer, allowing the customers accounts to be given access to his orher own accounts.

In system 900, the fingerprint database 960 includes fingerprint imagesor corresponding data for a plurality of angular positions for eachauthorized person. In some embodiments, the fingerprint database mayinclude only a single fingerprint image or corresponding data for eachauthorized person.

Reference is next made to FIG. 13, which illustrates another accesscontrol system 1300. System 1300 has a plurality of access controlmodules 1370, a fingerprint database 1360 and an authorization sequencedatabase 1372.

Fingerprint database 1360 includes a plurality of fingerprint records,each of which includes:

Field Contents Authorized person identifier An identifier for anauthorized person Fingerprint data An image of the authorized person'sfinger or corresponding data.

Authorization sequence database 1372 includes a plurality of sequencerecords, each of which includes:

Field Contents Authorized person identifier An identifier for anauthorized person Authorized angle sequence A sequence of angularpositions

System 1300 may be used to control access to an item, like systems 900and 1200. For each authorized person, a fingerprint record is recordedin the fingerprint database 1360 and a sequence record is recorded inthe authorization sequence database 1372.

To authenticate or identify a person as an authorized person, theprocessor in an access control module 1370 obtains a sequence offingerprint signals and assembles a sequence of angular positions andcorresponding fingerprint images (similar to step 1102 and 1104 ofmethod 1100 (FIG. 11)). The processor accesses the fingerprint database1360 to determine if each fingerprint image corresponds to the sameauthorized person. If not, the person is not authenticated as anauthorized person (similar to step 1106). The processor accesses theauthorization sequence database 1372 to determine if the sequence ofangular positions corresponds to the authorized angle sequence recordedfor the same authorized person. If so, the person is authenticated asthe authorized person identified by the matching authorized personidentifiers in the fingerprint database 1360 and the authorizationsequence database 1372.

The fingerprint database 1360 of system 1300 may be a fingerprintdatabase maintained by a third party. For example, an individual mayregister his or her fingerprint in fingerprint database 1360.Subsequently, the individual may register with to access an item securedwith system 1300. The individual may then record an authorized anglesequence in authorized sequence database 1372, which may be maintainedby the operator of system 1300 or by a third party.

In other embodiments, a system may include more than one fingerprintdatabase may be incorporated into a system, allowing individuals whohave registered their fingerprints with various fingerprint databases touse the system.

Some fingerprint databases do not include angular information forfingerprint data. In such systems, if a fingerprint is scanned at anyangle, it may be matched to a corresponding fingerprint that wasoriginally scanned at a different angle. System 1300 may be used withsuch systems. By determining the angular placement of a finger when afingerprint is scanned and independently verifying a fingerprint match,system 1300 allows an existing fingerprint database to be used with theadditional security offered by angular authorization sequences.

In the system described above, each authorized person records one ormore fingerprints for a single finger. In other embodiments, the personmay record one or more fingerprints for more than one finger, allowingauthorization sequences to incorporate both sequences of differentfingers and different angular positions for each finger in the sequence.

In some embodiments, an authorized sequence may include a sequence ofdifferent fingers, without requiring specific angular placement.

In some embodiments, it may be desirable to allow access only if two ormore persons are authenticated. In some embodiments, the person may beauthenticated independently. In other embodiments, an authorizedsequence may include fingerprints from each of the persons, requiringthem to cooperate to scan their fingers in an authorized sequence.

In the embodiments described above, one authorized angle sequence isrecorded for each authorized person. In other embodiments, two or moreauthorized angle sequences may be recorded for some or all of theauthorized persons. Each authorized sequence may be used to allow accessto the same item, or some authorized angle sequences may be used totrigger access to different items. For example, an authorized person mayuse different authorized angle sequences to obtain access to differentparts of a facility. In some embodiments, some angle sequences maytrigger specific functions. For example, a bank customer may have useone authorized angle sequence to obtain access to the person's bankaccounts at an ATM under normal conditions, but may use a differentauthorized angle sequence if the customer is being forced to access hisor her accounts under duress. The second authorized angle sequence maytrigger an emergency response, reduced balances being displayed for thecustomer's accounts, a reduced withdrawal limit being provided or acombination of these and other actions.

In some embodiments, a series of single use authorized angle sequencesmay be generated for an authorized person. The series of single useauthorized angle sequences are recorded in an authorized sequencedatabase and is also provided to the authorized person. Each time thatthe authorized person uses an access control system to access an item,the authorized person must use a different single authorized anglesequence. Once an authorized angle sequence has been used, it is nolonger valid.

The access control systems described above combine several securityfeatures to authenticate a person as an authorized person. A person isauthenticated if the person enters the correct biometric fingerprintdata as well as entering a correct sequence or code. Thus anunauthorized person who coincidentally has a fingerprint matching thatof an authorized person is unlikely to be authenticated because theunauthorized person will likely not know the authorization sequence forthe authorized person. An unauthorized person who knows the correctauthorization sequence is unlikely to be authenticated because theunauthorized person is unlikely to have the necessary fingerprint. Bycombining biometric and code based security concepts, the access controlsystems are more secure than systems that use only one securitytechnique.

Reference is next made to FIGS. 15 a and 15 b. The systems describedabove describe the use of a conductive finger to couple a drive signalfrom a bezel or bezel segment to a sensor die. In some cases, a fingerthat has been removed from a person will sufficiently couple a drivesignal to allow the severed finger to be used to authenticate a person.Typically, a person's heart beat causes fluctuations in the skinsurface, including the fingertips, which results in a rhythmic variationin the pressure between a finger and the sensor die. FIG. 15 aillustrates a fingerprint image obtained when a finger is pressedagainst a sensor die with less pressure. FIG. 15 b illustrates afingerprint image obtained when the finger is pressed against a sensordie with greater pressure. In some embodiments, the processor mayexamine some or all of a fingerprint image to determine if the width oflines 1502 is expanding and contracting within the heartbeat frequency atypical heart rate, and if not, then the processor may be configured torefuse to authenticate a person. In this manner, the processor may beable to refuse authentication if a severed finger is used.

Reference is next made to FIG. 16 a-16 c, which illustrate a fingerprintsensor 1602. Finger print sensor 1602 has continuous bezel 1606 that, insome embodiments, is made of a metal. Five finger guides 1607 a-1607 eare formed in the bezel to guide a user in properly positioning his orher finger in one of five angular positions, illustrated in FIG. 16 b asthe −90°, −45°, 0°, 45° and 90° positions. A drive signal injectionpoint 1616 a-1616 e is positioned in each finger guide 1607 a-1607 e.Optional ground points 1617 a-1617 e are positioned between the fingerguides 1607. Fingerprint sensor 1602 has a sensor die 1608 that isinsulated from the bezel 1608 by an insulator 1610.

Fingerprint sensor 1602 is suitable for use with embodiments accordingto systems 100 and 700 and the various access control systems describedabove.

In some embodiments, it may be desirable to reduce power consumption.Reference is next made to FIGS. 17 a, 17 b and 17 c, which illustrateseveral fingerprint sensors that include user presence detectionsystems. When a system is not use, the system may enter a low power modein which the user presence detection system is active, but otherfunctions are not active to reduce power consumption. Reduced powerconsumption may be particularly desirable in systems that are batterypowered, or powered by low power supplies such as USB ports. When a useris detected, the system is activated.

FIG. 17 illustrates a fingerprint sensing system 1700. Components ofsystem 1700 that correspond to the embodiments described above areidentified by similar reference numerals. Finger print sensor 1702 andcontroller 1704 are coupled together through communication links 1718and 1720. System 1700 includes an activity sensing sub-system comprisinga high gain block 1770. Die connection layer 1712 is coupled tocontroller 1704 through a high gain block 1770.

In operation, when system 1700 is not in use (i.e. has not been used forsome time period), controller 1704 puts system 1700 into a low powermode. In the low power mode, the controller 1704 may stop generating andinjecting drive signals, may stop acquiring and analyzing fingerprintsignals and may take other steps to reduce power consumption. When aperson touches sensor die 1718, the person will typically couple arelatively small signal into the sensor die. The small signal willtypically correspond to electrostatic and electromagnetic noisesurrounding the person, such as power line signals, static charges, etc.The coupled signal is amplified by the high gain block 1770, whichgenerates a “wake-up” signal 1780. In response to the wake-up signal1780, processor 1704 activates system 1700 into a normal operation modeand begins operating system 1700 as described above. During normaloperation, controller 1704 may turn off high gain block 1770 to reducepower consumption.

FIG. 18 illustrates another fingerprint sensing system 1800. Componentsof system 1800 that correspond to embodiments described above areidentified by similar reference numerals. System 1800 includes anactivity sensing subsystem, which comprises an optical transmitter 1872,an optical receiver 1874 and high gain block 1870. Like system 1700,system 1800 operates in a low power mode when the system is inactive. Inthe low power mode, optical transmitter 1872 (which may be a low powerLED or IR source) transmits light above the sensor die 1808. The lightis detected by the optical receiver 1874. If the beam of light is broken(typically be a finger being placed on the sensor die), and thus lightis not received at optical receiver 1874, high gain block 1870 generatesa wake-up signal 1880 and controller 1804 returns system 1800 to itsnormal operation mode. Optionally, the light signal transmitted byoptical transmitter 1872 may be pulsed to reduce power, and opticalreceiver 1874 synchronously detects the transmitted light.

Reference is next made to FIG. 19, which illustrates another fingerprintsensing system 1900. Components of system 1900 that correspond toembodiments described above are identified by similar referencenumerals. System 1900 includes an activity sensing block that includesan accelerometer or vibration sensor 1976 and a high gain block 1970.System 1900 has a low power mode in which high gain block 1970 monitorsaccelerometer 1976. Accelerometer 1976 is response to movement of thefingerprint sensor 1902 and generates a movement signal 1982corresponding to the movement of the fingerprint sensor. If the movementsignal 1982 indicates movement beyond a threshold, then high gain block1970 generates a wakeup signal 1980, in response to which the controller1904 returns system 1900 to it normal operation mode. By selecting thethreshold, system 1900 can be configured to wake up and return to itsnormal operation mode in response to a small vibration, repeated tappingon the sensor die by a finger or another vibration level.

The fingerprint sensing systems and access control systems may becombined with other security or authorization systems to control accessto an item. For example, in an ATM system, an access control system asdescribed above may be combined with a magnetic stripe or other scannerto allow bank customers to use either or both of a fingerprint basedaccess control system or a traditional bank card/passcode authenticationsystem.

In a time and attendance system used to track the presence of employeesat their places of employment (or other system requiring proof that aperson has attended a location), an access control system may be used totrack employees or other person upon entering and exiting a facility. Insome cases, one of the person's fingers (the index finger for example)may be used when entering the facility. A second finger (the middlefinger) may be used when leaving the facility. A third finger may beused to indicated distress or call for help, such as in a case where anunauthorized person is forcing an employee to give the unauthorizedperson access to the facility.

An access control system may also be used to provide access to hotelrooms and other locations, in place of or in combination with magneticor RFID based cards or keys. A user may scan in a fingerprint and recordan access sequence when registering at the hotel. The user may thenrepeat the access sequence at a fingerprint scanner at a room door toaccess the room.

The present invention has been described here by way of example only.Various modification and variations may be made to these exemplaryembodiments without departing from the spirit and scope of theinvention.

1. A method of operating an access control system, the methodcomprising: recording fingerprint data corresponding to one or morefingers of a particular authorized person; recording a sequence offinger positions for the particular authorized person; receiving aseries of fingerprint signals from a fingerprint sensor; determining asequence of angular positions corresponding to sequential fingerprintsignals in the series; determining if each of the fingerprint signalscorresponds to the recorded fingerprint data; determining if thesequence of angular positions corresponds to the recorded sequence offinger positions; and if the fingerprint signals corresponds to therecorded fingerprint data and the sequence of angular positionscorresponds to the recorded sequence of fingerprint positions, thenproviding an authorization signal.
 2. The method of claim 1 wherein theauthorization signal includes an identification of the authorizedperson.
 3. The method of claim 1 wherein the sequence of fingerpositions is specified by the authorized person.
 4. The method of claim1 wherein the fingerprint data corresponds to one or more fingers of theauthorized person positioned in multiple angular positions on afingerprint sensor.
 5. The method of claim 1 wherein the fingerprintdata corresponds to one or more fingerprints of the authorized person ina standard orientation.
 6. The method of claim 1 wherein the fingerprintdata and the sequence of finger positions of the particular authorizedperson are recorded in an authorized person record in a fingerprintdatabase that contains authorized person records for a plurality ofauthorized persons.
 7. The method of claim 6 including requiring theparticular authorized person to identify himself or herself prior toproviding the authorization signal.
 8. A method of operating an accesscontrol system, the method comprising: recording fingerprint datacorresponding to one or more fingers of a particular authorized personrotated at a variety of angles on a fingerprint sensor; recording asequence of angular finger positions for the particular authorizedperson; receiving a series of fingerprint signals from a fingerprintsensor, and if each of the fingerprint signals corresponds to therecorded fingerprint data and to the sequence of angular fingerpositions, then providing an authorization signal.
 9. The method ofclaim 8 wherein the authorization signal includes an identification ofthe particular authorized person.
 10. The method of claim 8 wherein thesequence of finger positions is specified by the particular authorizedperson.
 11. The method of claim 8 wherein the fingerprint data and thesequence of finger positions of the particular authorized person arerecorded in an authorized person record in a fingerprint database thatcontains authorized person records for a plurality of authorizedpersons.
 12. The method of claim 11 including requiring the particularauthorized person to identify himself or herself prior to providing theauthorization signal.
 13. A method of operating a fingerprint sensingsystem, the method comprising: providing a fingerprint sensor having asensor die and a bezel, wherein the bezel has a plurality of drivesignal injection points; injecting a drive signal into each of the drivesignal injection points; receiving a fingerprint signal from thefingerprint sensor, wherein the fingerprint signal corresponds to atleast one of the drive signals; and determining the drive signal ordrive signals to which the fingerprint signal corresponds.
 14. Themethod of claim 13 wherein the drive signal injection points are spacedabout the bezel.
 15. The method of claim 13 wherein the drive signalinjection points are located at various angular positions about thebezel.
 16. The method of claim 13 further including varying themagnitude of some or all of the drive signals to control asignal-to-noise ratio of the fingerprint signal.
 17. The method of claim13 further including varying the magnitude of some or all of the drivesignals to control lines and gaps in a fingerprint image obtained fromthe fingerprint signal.
 18. The method of claim 13 further includingdetermining an angular orientation of a finger positioned on thefingerprint sensor.
 19. The method of claim 13 further includingrepeating the steps of receiving a fingerprint signal and determiningthe drive signal or drive signals to which the fingerprint signalcorresponds and further including recording a sequence of drive signalscorresponding to the received fingerprint signals.
 20. The method ofclaim 13 wherein the drive signals are different from one another. 21.The method of claim 13 wherein the drive signals have temporallydistinct active and inactive phases.
 22. The method of claim 13 whereinthe drive signals have different shapes, each of which isdistinguishable from the other drive signals.
 23. A fingerprint sensingsystem comprising: a fingerprint sensor including: a bezel having aplurality of signal injection points; and a sensor die electricallyinsulated from the bezel; and a controller coupled to the fingerprintsensor to receive a fingerprint signal, wherein the controller includes:a plurality of drive signal blocks, wherein each drive signal block iscoupled to a corresponding signal injection point to inject a drivesignal into the corresponding signal injection point.
 24. The system ofclaim 23 wherein the bezel and sensor die are positioned to allow eachof the drive signals to be coupled to the sensor die by a finger incontact with the corresponding drive signal injection point and thesensor die.
 25. The system of claim 23 wherein each drive signal isunique.
 26. The system of claim 23 wherein each of the drive signals hasan active phase and an inactive phase, wherein only one drive signal isin is active phase at any particular time.
 27. The system of claim 25wherein each of the drive signals has an active phase and an inactivephase, wherein only one drive signal is in is active phase at anyparticular time.
 28. The system of claim 23 wherein the controller andthe fingerprint sensor are coupled through a wired communication link.29. The system of claim 23 wherein the controller and the fingerprintsensor are coupled through a wireless communication link.
 30. The systemof claim 23 wherein the bezel is formed of a conductive material. 31.The system of claim 23 wherein the bezel is formed of a conductivematerial selected from the group consisting of conductive plastics andmetal.
 32. The system of claim 23 wherein the bezel is a continuousbezel.
 33. The system of claim 23 wherein the bezel is a continuousbezel and wherein the bezel is grounded between at least some adjacentsignal injection points.
 34. The system of claim 23 wherein the bezel isa segmented bezel formed of a plurality of bezel segments and wherein atleast some of the signal injection points are provided on differentbezel segments.
 35. The system of claim 23 wherein the bezel is asegmented bezel formed of a plurality of bezel segments and wherein atleast some of the signal injection points are provided on differentbezel segments.
 36. The system of claim 23 wherein the bezel is groundedbetween at least some adjacent signal injection points.
 37. The systemof claim 23 wherein the bezel is a segmented bezel and wherein eachsignal injection point is provided on a different bezel segment.
 38. Anaccess control system comprising: a fingerprint sensor; a controllercoupled to the fingerprint sensor; and a fingerprint database coupled tothe controller, wherein the fingerprint database includes a plurality ofauthorized person records, each of the authorized person recordscontaining fingerprint data corresponding to an authorized person and anauthorized angle sequence.
 39. The system of claim 38, wherein thefingerprint data includes data corresponding to one or more of theparticular authorized person's fingerprints positioned at a plurality ofangular positions on the fingerprint sensor.